Steering wheels, because of their convenient location, typically include switches that actuate various motor vehicle accessories. Automobile horn switches are the most common of these. Traditionally, these horn switches have been relatively large buttons centrally located at the hub of the steering wheel. Their large size simplifies the operator's task of quickly locating and depressing the switch. See, for example, U.S. Pat. Nos.: 3,670,174, issued Jun. 13, 1972 to N. Sakakibara; 4,575,117, issued Mar. 11, 1986 to S. Uchida; 4,612,425, issued Sep. 16, 1986 to M. Kanai et al.; 4,638,131, issued Jan. 20, 1987 to R. L. Kidd et al.; 4,714,806, issued Dec. 22, 1987 to S. Inui et al.; and 4,872,364, issued Oct. 10, 1989 to K. Kaga et al.
Steering wheels are also the most convenient location for mounting a driver's side air bag. The air bag is often mounted at the hub of the steering wheel. However, the incorporation of an air bag unit within the steering wheel has made the inclusion of horn or other actuating switches within the steering wheel more complicated. Firstly, the air bag unit with its casing and cover door occupy a significant portion of the area within the steering wheel rim. Secondly, the cover door must be free to open upon expansion of the air bag.
Consequently, the horn switch has typically been relocated away from the hub and downsized to fit within the remaining space within the rim about the air bag cover door. See, for example, U.S. Pat. Nos.: 3,819,205, issued Jun. 25, 1974 to S. G. Dunford et al.; and 4,325,568, issued Apr. 20, 1982 to H. D. Clark et al. However, due to the historically conventional practice of locating a horn switch at the hub of a steering wheel, most drivers still feel more comfortable with a horn switch at the hub, particularly when faced with a panic situation. The conspicuous presence of a large pad at the hub further confuses drivers into mistakenly believing that the pad is the horn button.
Various arrangements have been disclosed for incorporating horn actuators, such as membrane switches, into air bag cover doors to thereby return the location of the horn switch to the hub. See, for example, Yoshio et al., Japanese Patent Application No. Hei 1[1989]-301461 and U.S. Pat. Nos.: 4,934,735, issued Jun. 19, 1990 to J. T. Embach; 5,002,306, issued Mar. 26, 1991 to T. Hiramitsu et al.; 5,062,661, issued Nov. 5, 1991 to L. J. Winget; 5,085,462, issued Feb. 4, 1992 to Q. E. Gualtier; 5,178,409, issued Jan. 12, 1993 to T. Hiramitsu et al.; and 5,186,490, issued Feb. 16, 1993 to G. V. Adams et al.
However, these arrangements are not entirely desirable from several standpoints. Firstly, many of these arrangements involve producing the horn actuator as an integral part of the air bag cover door. This requires constructing the horn actuator as a part of molding the cover door, resulting in an increase in the complexity and cost of manufacturing the cover door. Rather, it would be desirable to be able to mold the cover door as a separate component and thereafter to be able to quickly and easily attach or otherwise incorporate the horn actuator into the cover door.
Secondly, in some of these arrangements the presence of the horn actuator is visible on the exterior of the cover door which can be seen by the vehicle occupants. As a result, the horn actuator affects the aesthetic quality of the exterior surface of the cover door. Preferably, the horn actuator would not be perceptible on the exterior surface of the outer decorative cover so that the presence and/or location of the horn actuator can be indicated by an embossment or other marking on the exterior surface in accordance with the desired aesthetic look of the air bag cover door.
Thirdly, servicing (e.g., replacement) of the horn actuator and/or outer decorative cover in each of these arrangements requires disassembly of the air bag cover door that houses the air bag. Such disassembly of the cover door provides undesirable access to the air bag and other contents of the air bag module.
The prior art commonly meets certain of these three constraints, but not all. For example, the patent to Embach discloses a container for housing the air bag and a decorative outer cover disposed over the container. The container and outer cover both have tear seams that are aligned to permit deployment of the air bag. However, the container and outer cover are both secured by the same removable fastener such that, if the fastener is removed, both the outer cover and container can be removed thereby permitting undesirable access and potential unwanted tampering with the air bag.
Similarly, the patent to Gualtier discloses an air bag cover door that includes an inner cover and an outer cover fitted over the inner cover. The two covers have aligned tear seams formed therein, with the inner cover tear seam comprising perforations and the outer cover tear seam comprising a reduction in thickness of the outer cover. A horn switch is located between the inner and outer cover, either by securing it to the inner cover or by locating one contact on the inside surface of the outer cover and the other at a corresponding point on the outside surface of the inner cover. As with the patent to Embach, no arrangement is disclosed for providing removal of the outer cover and replacement of the horn switch while at the same time inhibiting access to the contents of the air bag module.
Another example is provided by the patent to Adams et al. Although the air bag cover disclosed therein includes a means for servicing and replacing the horn switch without permitting access to the air bag module, no provision is made for replacing the decorative air bag cover door without exposing the contents of the air bag module.
As a further example, the patents to Yoshio et al., Hiramitsu et al., and Winget each discloses a single cover for the air bag. Consequently, replacement of the cover requires that the contents of the air bag module be exposed, thereby permitting the unwanted access to the air bag.
As is made evident by Yoshio et al., it is known to use either screws or rivets to secure an air bag cover door to the base of the air bag module. Yoshio et al. shows various arrangements using either screws or rivets for this purpose. However, using screws allows undesirable access to air bag module contents. Using rivets, on the other hand, helps protect against tampering with the air bag, but makes replacement of the air bag cover door or horn actuator difficult because the rivets, which are intended as a permanent fastener, must be removed. In either event, the outer cover or horn actuator cannot be replaced without providing undesirable access to the interior of the air bag module.
Similarly, the construction shown in the Dunford et al. patent includes rivets used to secure the container to a metal bracket. The metal bracket, however, is secured along with the outer cover to the support plate via bolts threaded into nuts. Therefore, when the bolts are removed to permit replacement of the outer cover or access to the horn switch, the container can also be removed, thereby permitting access to the air bag.
U.S. Pat. No. 5,062,663, issued Nov. 5, 1991 to T. Satoh, also utilizes rivets. However, the air bag door cover comprises a pair of cut-in-half bodies forming the outer decorative cover and a thin resin film that holds the cut-in-half bodies together via protrusions in the cut-in-half bodies. Both the cut-in-half bodies and the resin film layer are secured to the case by a common set of rivets. Thus, in order to replace the outer cover (i.e., the cut-in-half bodies), the rivets must be removed, thereby providing access to the contents of the air bag module.
Thus, it would be advantageous to provide an air bag cover door that incorporates a horn actuator therein such that the outer cover and/or horn actuator can be serviced or replaced without providing access to the contents of the air bag module.